Drive Train noise

[Awann99]

For about a month every time I shift my 1969 gmc 1500 into drive it would make a loud ping noise. It has a th350. Two piece drive shaft and 12 bolt open diff. The noise will sometimes escalate to a load rattling as I drive. But it only makes the noise when I have my foot on the accelerator. If I coast the noice goes away. Now the noise sounds like the drive shaft is loose and going to fall out at any minute. I got under the truck and all the U joints are tight. So I’m stumped trying to find the source of the racket. Possible the carrier bearing any ways to check this? Thanks